This research program is designed to develop a new type of dental restorative material which simulates the appearance and physical properties of human enamel. One important property of this biomaterial should be its ability to seal through chemical adhesion its interfaces with hard oral tissues. Clinical use of a chemically adhesive material has the potential of, allowing a minimal removal of healthy tissue during the restoration of carious lesions, and reducing the incidence of secondary caries. A second important property sought with the new restorative is biocompatibility. One factor foreseen as a contribution to this property is the absence of low molecular weight organic compounds in the material's formulation. The microstructural concept involves micro-particles of synthetic hydroxyapatite, cemented by sub-microscopic layers of a polyelectrolytic complex. This complex has two basic polymeric components, fluoride salts or polyionenes (polycations) and sodium salts of poly (alkenoic acids) (polyanions). These two components will be adsorbed separately from dilute aqueous solution during wet growth of apatite crystals. Setting of the restorative material should occur upon mixing of a polycationic and a polyanionic hydrated powder (paste). The actual setting mechanism involves inter-diffusion of macromolecular segments (driven by coulombic charge interactions) to form a polyelectrolytic complex. The fundamental rationale behind the concept is based upon the peculiar molecular properties of polymers strongly adsorbed on solid surfaces. Given the importance of interfacial regions (the polyelectrolytic adsorbates), handling and physical properties of the restorative system are to be investigated as functions of size, surface area and surface electrical polarization in apatite micro-particles, and also as functions of molar mass and amount of adsorbed polyelectrolytes.